The present invention relates to electronic weighing devices and more particularly to a device for protecting the load cell of such electronic weighing devices.
Electronic scales are rapidly growing in pupularity for home, medical and industrial applications. Such scales utilize a load cell to convert an applied weight to a voltage level used to drive a readout device such as a numeric display. The load cell may, for example, comprise a piezoelectric crystal device which produces a voltage proportional to the stress applied to it by the weight. Such devices are extremely sinsitive and accurate.
A problem encountered with such scales is that the load cell is highly volnerable to being damaged and/or destroyed as a result of shock loads applied to it since such loads can far exceed the rated value of the load cell. The problem is complicated by the fact that for the overall scale range the total deflection of the load cell may be measured in thousandths of an inch. For example, the load cell of a physician's scale having a maximum capacity on the order of 300 lbs. is approximately 0.003 inch. This makes it extremely difficult if not impossible to provide mechanical stop means to protect the cell from being subjected to loads far in excess of its rated maximum value.
In view of the above, it is the principal object of the present invention to provide an improved electronic scale in which the load cell is protected from excessive loading or shock loading. A further object is to provide such protection without interfering with the weighing capability of the scale. A still further object is to provide such protection in a manner which is relatively inexpensive and may readily be incorporated into existing scale designs without requiring any drastic modifications.